Use annotations to refine code inspection
Code inspection and many other JetBrains Rider features largely rely on knowing behavior of language constructs to detect issues, suggest possible improvements, and help you in other ways.
However, this kind of analysis cannot detect everything. For example, if a method is designed as a formatting method no structural analysis will find a possible issue if a method invocation does not include necessary arguments.
In this and a lot of other cases, the JetBrains Rider's
JetBrains.Annotations is of a great help. By using attributes declared in this framework you can make JetBrains Rider analyze code the way you need it. For example, you can annotate a method with the
[StringFormatMethod] to indicate custom methods that work the same as
This being the simplest example, there are other helpful attributes with more complex use cases. You can find the full list of these attributes in the reference.
In most cases, code annotation attributes enable specific code inspections, for example:
StringFormatMethodAttributehelps detect misuses of string formatting methods.
NotNullAttributeare associated with the 'Possible 'null' assignment to entity marked with 'Value cannot be null' attribute' inspection. For more information, see Value and nullability analysis.
CannotApplyEqualityOperatorAttributeis bound to the 'Compare with '==' types marked by 'CannotApplyEqualityOperatorAttribute'' inspection
ContractAnnotationAttributecan be used to define contracts for your functions and turn on the corresponding inspections. For example, you can use
[ContractAnnotation("input:null => false")]to notify the consumers of the function
bool Foo(object input)that always returns
JetBrains Rider allows you to annotate code symbols in two ways:
You can annotate symbols in your source code as shown in the example above. In this case, you need to reference the
JetBrains.Annotationsnamespace in your project. For more information, see Annotations in source code.
Even if you do not have access to sources, you can annotate symbols in compiled library code. For more information, see External annotations.